mat·ri·line 
(mătrə-līn′)
(mătrə-līn′)n.
A line of descent traced through the maternal side of a family.
- on the order of
- on the other hand
- on the outs
- on the part of
- on the prowl
- on the qui vive
- on the rack
- on the rag
- on-the-record
- on the right foot
- on the road
- on the rocks
- on the ropes
- on the run
- on the same wavelength
- on-the-scene
- on the shelf
- on the side
- on the sly
- on the spectrum
- on the spot
- on the square
- on the street
- on the strength of
- on the string